The present invention relates to a method for operating an internal combustion engine.
More particularly, it relates to a method of operating of an internal combustion engine which has an exhaust gas conduit provided with an additional component, in particular a turbine and a turbocharger, in which at high throughput the mixture is changed to be richer, and based on at least one main filling signal sensor a main filling signal, and based on of at least one substitute filling signal sensor at least one substitute filling signal is determined.
A method of this type is known. It is based on the experience that for example a turbocharger in an exhaust gas conduit can be damaged at very high exhaust gas temperatures. High exhaust gas temperatures also occur mainly at a very high air throughput or in other words at a high rotary speed. In order to lower the exhaust gas temperature in this operational condition the mixture at very high throughput is enriched. The excess of fuel is evaporated and provides a cooling of the exhaust gas which exits the combustion chambers.
In known methods the required air filling in the combustion chambers for obtaining an optimal mixture is determined on the basis of a main filling signal sensor. In order to perform the operation also in the case of a failure of the main filling signal sensor it is proposed in the inventive method to determine a substitute filling signal which is obtained from a substitute filling signal sensor. If the main filling signal and the substitute filling signal exceed more than a predetermined error factor, the calculation of the filling of the combustion chamber is performed on the basis of the signal of the substitute filling signal sensor.
When the known method was performed, it was however determined that damages to the turbocharger arranged in the exhaust gas conduit by excessively high temperatures of the exhaust gas can not be completely excluded.
Accordingly, it is an object of the present invention to provide a method of the above mentioned type, which avoids the disadvantages of the prior art.
More particularly, it is an object of present invention to provide a method of the above mentioned type, which is performed so that the service life of the turbocharger or another additional component arranged in the exhaust gas conduit of the internal combustion chamber is as long as possible.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a method in which the substitute filling signal is converted into a control signal for at least one value selected from the group consisting of an air supply, a fuel supply, and an ignition time point, when it is greater than the main filling signal by at least a protective factor, and a protective factor is selected so that at high throughput the change of the mixture consist of enriching.
The inventive solutions is based on the following considerations. When the main filling signal sensor supplies a signal which is too small, a filling of the combustion chambers of the internal combustion engine is performed, which is smaller than the actual filling. Correspondingly also the quantity of the injected fuel is reduced. When such an internal combustion engine operates with the high throughput and for protection of turbo charger the mixture is fattened, based on this actually poor mixture is achieved. With a main filling signal sensor which provides a main filling signal which is smaller than that corresponding to the actual filling, or in other words at high throughput, the mixture is not always fattened, or in other words operated with fuel surplus, but instead from a too poor condition is brought into a substantially richer condition.
The inventive method is as follows. In order to determine more reliably that at high throughput the mixture actually is fattened (the internal combustion engine is operated in a too fattened condition with fuel surplus), it is not necessary to do anything else but to determine a maximum value from a substitute filling signal and a main filling signal and to use the substitute filling signal for computation of the filling of the combustion chamber of the internal combustion engine when the substitute filling signal is greater than the main filling signal by a protective factor. The expression xe2x80x9cprotective factorxe2x80x9d is selected so that it deals with a factor which provides protection of the additional component arranged in the exhaust gas conduit. The value of the protective factor is determined simply from the requirement, that at constant enrichment in high load region in each case a substantial fattening must be guaranteed. In practice the protective factor is so small that already with a low deviation it is switched to the substitute filling signal.
The inventive process therefore guarantees that with a high throughput also actually a fattening of the mixture is performed and thereby the temperature in the exhaust gas of the internal combustion engine is reduced and the additional components arranged in the exhaust gas conduit are protected from a temperature-dependent damage.
In accordance with another feature of the present invention, it can be for example provided that when the main filling signal differs by at least an error factor from the substitute filling signal, the main filling signal is recognized as defective and the substitute filling signal instead of the main filling signal is converted into a control signal for at least one value selected from the group consisting of the air supply, fuel supply or ignition time point, wherein the protective factor is substantially smaller than the error factor.
The use of the substitute filling signal is performed also when the main filling signal is not defective in its own sense. As a defective main filling signal namely conventionally a relatively great deviation from the substitute filling signal is considered, since this deviation is calculated from the sum of the additional tolerances of the main filling signal sensor and the substitute filling sensor. In accordance with the present invention it is determined that a mixture which is too poor and makes impossible the fattening required at high throughput is provided at deviations between the substitute filling signal and the main filling signal which is substantially smaller than the sum of the above mentioned tolerances.
In an especially preferable quantitative example, the error factor is located in the region of +/xe2x88x9225% and the protective factor is located in the region +25%.
The main filling signal sensor can be formed for example as a heating wire air measuring sensor. Such sensor has a heated element which is located in the air stream to be measured and is cooled by the latter. Conventionally, the heated element is a part of an electrical bridge circuit, and is held by a flowing stream at constant upper temperature with respect to the temperature of the aspirated air. The required heating stream is a value which is simply processed for the inventive method, for the air mass aspirated by the internal combustion engine.
In accordance with a further embodiment of the invention, it is further proposed that the substitute filling signal is obtained from a position sensor of a throttle flap and in some cases from a rotary speed sensor and in some cases from a pressure sensor in the aspiration pipe. The corresponding sensors are available in numerous internal combustion engines and allow determination of the filling of the internal combustion engine in a relatively simple and precise manner.
The present invention also deals with a computer program, which is suitable for performing the above mentioned method when a computer is utilized. It is especially advantageous when the computer program is stored in a storage, for example a flash memory.
Finally, the invention also deals with a control and/or regulation device for operation of an internal combustion engine, in which additional components, in particular a turbine and a turbo charger are arranged in its exhaust gas conduit, with means which in the event of a high throughput produce a control signal for changing the mixture in direction toward reacher mixture with means for determination of a main filling signal and with means for determination of a substitute filling signal.
For protecting the additional components arranged in the exhaust gas conduit in the case of high throughput from excessively high temperatures, it is proposed in the inventive device to convert the substitute filling signal into a control signal for at least one value selected from the group consisting of air supply, fuel supply and an ignition time point, when it is greater than the main filling signal by a protective factor, and the protective factor is selected so that the change of the mixture resides in its fattening.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.